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Old January 27, 2015, 07:54 AM
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Actually I think I see what's going on. We're both saying the same thing it's just I'm trying to simplify things down into slightly more digestible terms while Anandtech is quoting directly from the NVIDIA technical briefing. Maybe something is getting garbled in my translation.

So yes, both partitions can be accessed through proper interleaving (which is the job of the driver for the most part) in situations where allocations are over 3.5GB. I think the main issue is that NVIDIA's stated 224GB/s of bandwidth will ONLY be available in higher memory situations and even then, if there's a hiccup in the heuristics bandwidth could be further reduced. That's a pretty narrow window IMO, especially considering the card will be operating with 196GB/s of bandwidth in the vast majority of games.
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Old January 27, 2015, 08:28 AM
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Originally Posted by SKYMTL View Post
Actually I think I see what's going on. We're both saying the same thing it's just I'm trying to simplify things down into slightly more digestible terms while Anandtech is quoting directly from the NVIDIA technical briefing. Maybe something is getting garbled in my translation.

So yes, both partitions can be accessed through proper interleaving (which is the job of the driver for the most part) in situations where allocations are over 3.5GB. I think the main issue is that NVIDIA's stated 224GB/s of bandwidth will ONLY be available in higher memory situations and even then, if there's a hiccup in the heuristics bandwidth could be further reduced. That's a pretty narrow window IMO, especially considering the card will be operating with 196GB/s of bandwidth in the vast majority of games.
We need thorough frametime testing when VRAM hits > 3.5 GB and <= 4GB to see the real world effects of this issue. Already there are indications that frametimes could be affected in few cases.

Page 2 - Investigating the GTX 970: Does Nvidia?s GPU have a memory problem? | ExtremeTech

As for opinion imo Nvidia misled the press and the public on specs. I do not believe their explanation that marketing got it wrong. When you are talking about a high technology product the specs come from the product design team not some person who does not know anything about the design and engineering. The fact that this explanation came after 4 months and only after it was found by some programmer does not give any confidence in their statements.

btw Jen Hsun himself is an engineer and takes a lot of pride in Nvidia's engineering. I do not believe that he did not know the details of the product that he unveiled with so much pride.

https://www.youtube.com/watch?v=LUdP8_NQmgk

I am quite sure there was a choice present before Nvidia - to mention the correct specs at launch and risk maybe lower sales or let it be as they did and address it only if it was found and became necessary. They chose the latter.

Last edited by Fragman; January 27, 2015 at 08:42 AM.
  #43 (permalink)  
Old January 27, 2015, 08:42 AM
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I'm actually on the fence about it. On one hand the situation is almost too perfect; ie: somehow, several teams at NVIDIA "missed" the fact that in no fewer than four documents submitted to the press there was a glaring error. That error being the number of active ROPs. Had that been addressed, many of us would have started asking how other subsystems were affected. Convenient? Yup. However, there's just no way to prove what happened.

On the flip side of that coin, having the knowledge of this potential shortcoming hasn't affected the GTX 970's performance in any way. Its 4K performance in SLI is what it is. Its 1440P single card performance is what it is. Had any of these been adversely affected, a red flag would have been raised from day one. Hence, I think that for the time being, the driver-based algorithm seems to have been doing its job in a transparent manner.

As for the frametimes, thus far I haven't seen any untowards problems and I've literally been up all night testing. We can't forget that frametime deltas between the GTX 980 and GTX 970 WILL be present since the 970 doesn't have the raw throughput of its sibling so it will naturally take a longer time to render frames.

One thing that I do want to mention is that in my testing, the R9 290X is an absolute BEAST when it comes to memory-intensive applications. We saw that already in the GTX 970 SLI review and it hasn't changed one iota.
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Old January 27, 2015, 09:13 AM
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One thing that I do want to mention is that in my testing, the R9 290X is an absolute BEAST when it comes to memory-intensive applications. We saw that already in the GTX 970 SLI review and it hasn't changed one iota.
Thats what gets me really excited about the R9 390X and that massive memory bandwidth due to HBM. Combine that with the Tonga (GCN 1.2) color compression memory bandwidth efficiency improvements and we are talking of > 50% memory bandwidth improvement per sp or per CU even with the 4096 sp. The only thing I want to know is has AMD been able to go with 6 GB HBM. There is nothing stopping them from having 6 stacks (of 4 Hi ) HBM for a massive 768 GB/s.

I doubt AMD will restrict their flagship GPU to 4GB. They have been having higher VRAM then Nvidia for the past 3 generations. GTX 580 vs HD 6970, GTX 680 vs HD 7970, GTX 780 Ti vs R9 290X. Either they have a hybrid memory system with 4GB HBM (4 stacks of 4 Hi) + maybe 4GB GDDR5 or they are going to push for 6GB HBM if they want to keep a single memory system type.

Last edited by Fragman; January 27, 2015 at 09:32 AM.
  #45 (permalink)  
Old January 27, 2015, 09:30 AM
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fwiw a user posting his experience with GTX 970 SLI and 1440p.

http://www.reddit.com/r/buildapc/com..._sli_at_1440p/
  #46 (permalink)  
Old January 27, 2015, 09:40 AM
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That is really odd. We've tested it to death....with frametimes:

http://www.hardwarecanucks.com/forum...review-13.html

http://www.hardwarecanucks.com/forum...review-14.html

I do want to mention that Far Cry 4 does have what seems to be an odd allocation issue where some solutions (like AMD's R9 290-series) get completely saturated which causes stuttering for some reason. This was present in Far Cry 3 as well. I'm not sure if it affects the GTX 970 SLI as well but this is a horrible situation with yet another Ubisoft game.

Another thing to mention is that "above 3.5GB" could mean "above 4GB" as well. As we've discussed, that may cause the GPU to call on system memory through the PCIe bus which causes massive framerate drops.

We can't point at every situation where folks are experiencing framerate drops and arbitrarily blame it on the GTX 970's partitioning. :)
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Old January 27, 2015, 09:57 AM
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Originally Posted by SKYMTL View Post
That is really odd. We've tested it to death....with frametimes:

http://www.hardwarecanucks.com/forum...review-13.html

http://www.hardwarecanucks.com/forum...review-14.html

I do want to mention that Far Cry 4 does have what seems to be an odd allocation issue where some solutions (like AMD's R9 290-series) get completely saturated which causes stuttering for some reason. This was present in Far Cry 3 as well. I'm not sure if it affects the GTX 970 SLI as well but this is a horrible situation with yet another Ubisoft game.

Another thing to mention is that "above 3.5GB" could mean "above 4GB" as well. As we've discussed, that may cause the GPU to call on system memory through the PCIe bus which causes massive framerate drops.

We can't point at every situation where folks are experiencing framerate drops and arbitrarily blame it on the GTX 970's partitioning. :)
I agree you tested. But given the new info you might want to track VRAM usage too to see if you are accessing the last 0.5 GB. I am fairly sure you can hit the window where usage is between 3.5 GB and 4GB and then you might see the problems that others experience. I do feel for the press. Your job keeps getting trickier day by day with the stuff these GPU vendors keep pulling. First it was frametimes and now this. Who knows what else you have to face in future ? Someday in the future enthusiast hardware testing might become so complicated it might require a bachelors degree program. jk

This issue with GTX 970 is even more disconcerting as Nvidia is touting DSR as a major feature. We know that DSR could push VRAM usage above 3.5GB even at 1080p. A lot of valid reason for users to be concerned.

Last edited by Fragman; January 27, 2015 at 10:03 AM.
  #48 (permalink)  
Old January 27, 2015, 10:12 AM
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This issue with GTX 970 is even more disconcerting as Nvidia is touting DSR as a major feature. We know that DSR could push VRAM usage above 3.5GB even at 1080p. A lot of valid reason for users to be concerned.
100% agreed with this. Guess what I'm testing right now. ;)
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Old January 27, 2015, 10:40 AM
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Originally Posted by Fragman View Post
fwiw a user posting his experience with GTX 970 SLI and 1440p.

http://www.reddit.com/r/buildapc/com..._sli_at_1440p/
Yeah I have to agree with his conclusions.

I tested a bit more with Skyrim Mods and Shadow of Mordor High Textures and there are hichups when you turn the camera.

This only happens above 3.5GB.

It isn't as bad as some are claiming but the stutter is noticeable above 3.5GB.

I think it is best to avoid the 970 for those who want to run VRAM intensive things like Modded Skyrim @ 1440p or above. Might be better to go for a R9 290.

For most games like battlefield, starcraft ect @ 1080p -1440p, it shouldn't really be an issue.
  #50 (permalink)  
Old January 27, 2015, 11:07 AM
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I hate to say this but I have yet to see a game or architecture that doesn't stutter when it needs to quickly load high resolution assets from a fast camera turn. This is certainly not unique to the 970.
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